Production method and application of graphite phase carbon nitride electrostatic spinning antibacterial food packaging paper

Abstract

The invention relates to the technical field of paper coatings, in particular to a production method and application of graphite-phase carbon nitride electrostatic spinning antibacterial food packaging paper.The production method comprises the following steps that graphite-phase carbon nitride is prepared through high-temperature calcination; carrying out thermal oxidation stripping operation; introducing a hydrophobic material to prepare a coating; the antibacterial food packaging paper is prepared through film covering of an electrostatic spinning device. The antibacterial film can be widely applied to packaging of various products needing antibacterial preservation and hydrophobicity, such as fresh fruits, medicines, medical instruments or cosmetics.

Description

Technical Field

[0001] This invention relates to the field of paper coating technology, specifically to a production method and application of graphite phase carbon nitride electrospun antibacterial food packaging paper. Background Technology

[0002] Traditional packaging materials are struggling to meet the rapidly evolving needs of the logistics industry. Therefore, researching a packaging material that is "green, environmentally friendly, low-cost, has no side effects, and has significant antibacterial effects" has become an urgent requirement.

[0003] g-C3N4 is a low-cost and environmentally friendly photocatalyst, whose bulk and layered structures provide it with good stability. The g-C3N4 antibacterial agent kills bacteria by generating reactive oxygen species that directly act on the bacterial cell membrane, DNA, and RNA through electron-hole pair redox reactions, avoiding secondary contamination of the antibacterial agent itself. By appropriately loading the g-C3N4 antibacterial agent onto the surface of packaging materials, the antibacterial time can be effectively extended. However, it is susceptible to mold growth due to environmental temperature and humidity, which poses a significant threat to the quality of packaged food. To address the challenges of the distribution environment, a combination of PDMS (reducing surface free energy) and hydrophobic SiO2 (increasing surface roughness) can enhance hydrophobic properties.

[0004] Paper-based materials are widely used in the transport packaging of fresh food due to their advantages such as recyclability, biodegradability, environmental friendliness, and non-toxicity. Therefore, combining the g-C3N4 antibacterial agent with paper-based materials, and integrating it with hydrophobic materials, can meet the current needs of fresh food packaging. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor hydrophobicity and poor antibacterial properties of existing food packaging materials, and to provide a production method and application of graphite phase carbon nitride electrospun antibacterial food packaging paper. This invention prepares graphite phase carbon nitride through high-temperature calcination; then increases the reactivity through thermal oxidation peeling; increases the hydrophobic effect by introducing hydrophobic materials; and finally prepares hydrophobic graphite phase carbon nitride coated food packaging paper by electrospinning.

[0006] Specifically, the following technical solution is used to achieve the following: A method for producing graphite phase carbon nitride electrospun antibacterial food packaging paper, including the following steps: (1) preparing graphite phase carbon nitride by high-temperature calcination; (2) performing thermal oxidation peeling operation; (3) introducing hydrophobic materials to prepare coating; (4) preparing antibacterial food packaging paper by electrospinning device coating.

[0007] Furthermore, the high-temperature calcination preparation of graphitic carbon nitride involves weighing 10-20 parts by weight of urea and calcining it in a tube furnace for 1-3 hours to obtain powdered graphitic carbon nitride.

[0008] Furthermore, the high-temperature calcination is carried out under a nitrogen atmosphere.

[0009] Furthermore, the high-temperature calcination is carried out at a rate of 2-8°C / min, increasing the temperature from room temperature to 550°C.

[0010] Furthermore, the thermal oxidation stripping operation is as follows: S1. Disperse the graphitic carbon nitride obtained by high-temperature calcination in deionized water; S2. Add 1-2 parts by mass of K2S2O8, stir thoroughly, and then adjust the pH to 12 with 0.1-1 mol / L KOH solution. S3. Stir the mixture prepared in S2 in a water bath at 80-100℃ for 6 h, then sonicate for 1-5 h, centrifuge to discard the supernatant, and wash the precipitate with deionized water until neutral. S4. After freeze-drying, g-C3N4 nanosheets were obtained.

[0011] Furthermore, the hydrophobic material is a combination of PDMS and SiO2, specifically SiO2-PDMS.

[0012] Furthermore, the coating is prepared by ultrasonically dispersing 20-30 parts of g-C3N4 nanosheets obtained by thermal oxidation exfoliation in 100 parts of n-hexane solvent, adding PDMS, hydrophobic nano-SiO2 and curing agent in a ratio of 10:2:1, and stirring until uniform.

[0013] Furthermore, the curing agent is a dimethylsiloxane solution containing hydrogen-terminated groups.

[0014] Furthermore, the electrospinning device is used to prepare food packaging paper by injecting the coating into the electrospinning solution chamber, setting the spinning voltage to 10-20kV, the spinning speed to 2-15mm / h, the receiving distance to 10-20cm, the needle diameter to 0.5-1.2mm, the syringe capacity to 10ml, the spinning time to 1-5h, and drying in vacuum for 10-30h to obtain hydrophobic graphite phase carbon nitride coated food packaging paper.

[0015] Furthermore, the food packaging paper has a basis weight of 150-250 g / m³. 2 Corrugated paper.

[0016] The technical principle of this invention is as follows: (1) Taking advantage of the property that reactive oxygen species generated by the metal-free polymeric two-dimensional semiconductor material g-C3N4 under light source excitation can kill bacteria, it is used as a novel antibacterial material to replace traditional chemical antibacterial agents in antibacterial packaging. It is green and environmentally friendly, has a long-lasting effect, and does not produce drug resistance. The block g-C3N4 is exfoliated into carboxyl-rich g-C3N4 nanosheets by ultrasonic-assisted thermal oxidation exfoliation, which enhances its photocatalytic activity and improves its dispersibility and stability.

[0017] (2) By combining the method of reducing the surface free energy of PDMS and changing the PDMS coating structure through electrospinning to increase the surface micro-roughness, a CNNS / antibacterial food packaging paper with both stability and hydrophobicity was prepared with a ratio of PDMS:SiO2:curing agent of 10:2:1, and its water contact angle reached 145°.

[0018] (3) By combining electrospinning technology, scanning electron microscopy (SEM) images showed that a highly interwoven fiber network structure was formed on the substrate surface. Compared with conventional coating processes, this electrospinning strategy significantly increased the specific surface area of ​​the material. At the same time, the resulting PDMS fibers exhibited excellent light reflection properties, which could effectively enhance the light capture efficiency of g-C3N4 in the composite system. Microscale SEM observation further showed that the fiber diameter was distributed in the range of 150 nm to 300 nm. This size distribution was mainly affected by two factors: a) the G20 specification needle (inner diameter 0.58 mm) used tended to form finer fibers; b) the introduction of g-C3N4 not only changed the properties of the spinning solution, but the mass increase brought about by its loading also interfered with the stability of the Taylor cone and the fiber forming process. In addition, the fiber surface showed significant roughening characteristics. This micromorphology originated from the uniform dispersion of g-C3N4 particles inside, thus confirming the successful loading of g-C3N4 in PDMS fibers.

[0019] Beneficial effects Compared with the prior art, the present invention has the following advantages: First, graphitic carbon nitride nanosheets are prepared through high-temperature calcination and thermal oxidation exfoliation. Then, a paper-based hydrophobic graphitic carbon nitride electrospun antibacterial coating is prepared by compounding PDMS and hydrophobic SiO2. Finally, an electrospinning coating process is used to break down the spinning solution into nanofibers, which are then stacked layer by layer on the paper substrate to form a uniform film. Furthermore, all materials used in this invention are green, environmentally friendly, non-toxic, and harmless, conforming to the green development policy. It can be widely used in the packaging of various products requiring antibacterial preservation and hydrophobicity, such as fresh fruits, pharmaceuticals, medical devices, or cosmetics. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of the present invention; Figure 2The antibacterial effects of the hydrophobic graphitic carbon nitride coating on food packaging paper prepared in Example 4 of this invention under dark and light conditions were obtained. Figure 3 The surface scanning electron microscope image of the food packaging paper with the hydrophobic graphite phase carbon nitride coating obtained in Example 4 of this invention; Figure 4 Scanning electron microscope image of graphitic carbon nitride nanosheets prepared in Example 4 of this invention; Figure 5 Water contact angle diagram of the food packaging paper with hydrophobic graphite phase carbon nitride coating obtained in Example 4 of this invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be described in detail below with reference to several embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 1. Preparation of graphitic carbon nitride (g-C3N4, CN) by thermal polycondensation: 10g of urea was ground evenly and transferred to an alumina crucible, which was then sealed with aluminum foil. Under a nitrogen atmosphere, the crucible was placed in a tube furnace and heated from room temperature to 550℃ at a rate of 2℃ / min, and calcined at this temperature for 1 hour. After natural cooling to room temperature, a pale yellow powder was obtained for later use.

[0023] 2. Preparation of g-C3N4 nanosheets (CNNS) by thermal oxidation exfoliation: 10 g CN was dispersed in 500 g deionized water and sonicated for 30 min. 1 g K2S2O8 was added and stirred thoroughly. The pH of the system was adjusted to 12 with 0.1 mol / L KOH solution. The mixture was stirred in an 85℃ water bath for 6 h, followed by sonication for 1 h. The supernatant was discarded by centrifugation, and the precipitate was washed with deionized water until neutral and then freeze-dried to obtain CNNS for later use.

[0024] 3. Finally, prepare the paper-based hydrophobic antibacterial coating: Take 20g of CNNS and ultrasonically disperse it in 100g of n-hexane. Add PDMS and hydrophobic nano-SiO at a mass ratio of 10:2:1. 2 The curing agent and the homogeneous mixture form an electrospinning coating.

[0025] 4. The coating is deposited on the paper surface using electrospinning technology. The coating is then injected into the electrospinning solution chamber. The spinning voltage is set to 10kV, the spinning speed to 2mm / h, the receiving distance to 10cm, the needle diameter to 0.5mm, the syringe capacity to 10ml, and the spinning time to 1h. The paper is then dried in a vacuum for 10h to obtain hydrophobic graphite phase carbon nitride coated food packaging paper.

[0026] Example 2 1. Preparation of graphitic carbon nitride (g-C3N4, CN) by thermal polycondensation: 20g of urea was ground evenly and transferred to an alumina crucible, which was then sealed with aluminum foil. Under a nitrogen atmosphere, the crucible was placed in a tube furnace and heated from room temperature to 550℃ at a rate of 8℃ / min, and calcined at this temperature for 3 hours. After natural cooling to room temperature, a pale yellow powder was obtained for later use.

[0027] 2. Preparation of g-C3N4 nanosheets (CNNS) by thermal oxidation exfoliation: 10g CN was dispersed in 500g deionized water and sonicated for 30 min. 2g K2S2O8 was added and stirred thoroughly. The pH of the system was adjusted to 12 with 1 mol / L KOH solution. The mixture was stirred in a 100℃ water bath for 6 h, followed by sonication for 5 h. The supernatant was discarded by centrifugation, and the precipitate was washed with deionized water until neutral and then freeze-dried to obtain CNNS for later use.

[0028] 3. Finally, prepare the paper-based hydrophobic antibacterial coating: Take 20g of CNNS and ultrasonically disperse it in 100g of n-hexane. Add PDMS and hydrophobic nano-SiO at a mass ratio of 10:2:1. 2 The curing agent and the homogeneous mixture form an electrospinning coating.

[0029] 4. The coating is deposited on the paper surface using electrospinning technology. The coating is injected into the electrospinning solution chamber. The spinning voltage is set to 20kV, the spinning speed to 15mm / h, the receiving distance to 20cm, the needle diameter to 1.2mm, the syringe capacity to 10ml, and the spinning time to 5h. The paper is then dried in a vacuum for 30h to obtain hydrophobic graphite phase carbon nitride coated food packaging paper.

[0030] Example 3 1. Preparation of graphitic carbon nitride (g-C3N4, CN) by thermal polycondensation: 15g of urea was ground evenly and transferred to an alumina crucible, which was then sealed with aluminum foil. Under a nitrogen atmosphere, the crucible was placed in a tube furnace and heated from room temperature to 550℃ at a rate of 4℃ / min, and calcined at this temperature for 2 hours. After natural cooling to room temperature, a pale yellow powder was obtained for later use.

[0031] 2. Preparation of g-C3N4 nanosheets (CNNS) by thermal oxidation exfoliation: 10 g CN was dispersed in 500 g deionized water and sonicated for 30 min. 1.5 g K2S2O8 was added and stirred thoroughly. The pH of the system was adjusted to 12 with 0.5 mol / L KOH solution. The mixture was stirred in a 90℃ water bath for 6 h, followed by sonication for 3 h. The supernatant was discarded by centrifugation, and the precipitate was washed with deionized water until neutral and then freeze-dried to obtain CNNS for later use.

[0032] 3. Finally, prepare the paper-based hydrophobic antibacterial coating: Take 20g of CNNS and ultrasonically disperse it in 100g of n-hexane. Add PDMS and hydrophobic nano-SiO at a mass ratio of 10:2:1. 2 The curing agent and the homogeneous mixture form an electrospinning coating.

[0033] 4. The coating is deposited on the paper surface using electrospinning technology. The coating is then injected into the electrospinning solution chamber. The spinning voltage is set to 15kV, the spinning speed to 8mm / h, the receiving distance to 15cm, the needle diameter to 1mm, the syringe capacity to 10ml, and the spinning time to 3h. The paper is then dried in a vacuum for 20h to obtain a hydrophobic graphite phase carbon nitride coated food packaging paper.

[0034] Example 4 1. Preparation of graphitic carbon nitride (g-C3N4, CN) by thermal polycondensation: 20g of urea was ground evenly and transferred to an alumina crucible, which was then sealed with aluminum foil. Under a nitrogen atmosphere, the crucible was placed in a tube furnace and heated from room temperature to 550℃ at a rate of 2℃ / min, and calcined at this temperature for 3 hours. After natural cooling to room temperature, a pale yellow powder was obtained for later use.

[0035] 2. Preparation of g-C3N4 nanosheets (CNNS) by thermal oxidation exfoliation: 10 g CN was dispersed in 500 g deionized water and sonicated for 30 min. 2 g K2S2O8 was added and stirred thoroughly. The pH of the system was adjusted to 12 with 0.1 mol / L KOH solution. The mixture was stirred in a 95℃ water bath for 6 h, followed by sonication for 3 h. The supernatant was discarded by centrifugation, and the precipitate was washed with deionized water until neutral and then freeze-dried to obtain CNNS for later use.

[0036] 3. Finally, prepare the paper-based hydrophobic antibacterial coating: Take 20g of CNNS and ultrasonically disperse it in 100g of n-hexane. Add PDMS and hydrophobic nano-SiO at a mass ratio of 10:2:1. 2 The curing agent and the homogeneous mixture form an electrospinning coating.

[0037] 4. The coating is deposited on the paper surface using electrospinning technology. The coating is injected into the electrospinning solution chamber. The spinning voltage is set to 20kV, the spinning speed to 2mm / h, the receiving distance to 20cm, the needle diameter to 0.8mm, the syringe capacity to 10ml, and the spinning time to 3h. The paper is then dried in a vacuum for 30h to obtain hydrophobic graphite phase carbon nitride coated food packaging paper.

[0038] Example 5 1. Preparation of graphitic carbon nitride (g-C3N4, CN) by thermal polycondensation: Grind 10-20g of urea evenly, transfer it to an alumina crucible, and seal it with aluminum foil. Under a nitrogen atmosphere, place the crucible in a tube furnace and heat it from room temperature to 550℃ at a rate of 2-8℃ / min, then calcine at this temperature for 1-3 hours. After naturally cooling to room temperature, a pale yellow powder is obtained for later use.

[0039] 2. Preparation of g-C3N4 nanosheets (CNNS) by thermal oxidation exfoliation: 10 parts of CN were dispersed in 500g of deionized water and sonicated for 30 min. 1g of K2S2O8 was added and stirred thoroughly. The pH of the system was adjusted to 12 with 0.2 mol / L KOH solution. The mixture was stirred in a 100℃ water bath for 6 h, followed by sonication for 2 h. The supernatant was discarded by centrifugation, and the precipitate was washed with deionized water until neutral and then freeze-dried to obtain CNNS for later use.

[0040] 3. Finally, prepare the paper-based hydrophobic antibacterial coating: Take 20g of CNNS and ultrasonically disperse it in 100g of n-hexane. Add PDMS and hydrophobic nano-SiO at a mass ratio of 10:2:1. 2 The curing agent and the homogeneous mixture form an electrospinning coating.

[0041] 4. The coating is deposited on the paper surface using electrospinning technology. The coating is injected into the electrospinning solution chamber. The spinning voltage is set to 20kV, the spinning speed to 2mm / h, the receiving distance to 15cm, the needle diameter to 1.2mm, the syringe capacity to 10ml, and the spinning time to 1h. The paper is then dried in a vacuum for 15h to obtain hydrophobic graphite phase carbon nitride coated food packaging paper.

[0042] The food packaging paper prepared according to the embodiments is described below in conjunction with the accompanying drawings: The antibacterial effects of the hydrophobic graphitic carbon nitride coated food packaging paper prepared in Example 2 under both dark and light conditions are as follows: Figure 2 As shown, under light conditions, the product achieved an antibacterial effect of over 95% against three pathogenic bacteria, indicating that the product meets the antibacterial requirements for food packaging preservation paper.

[0043] The surface scanning electron microscope (SEM) image of the food packaging paper with a hydrophobic graphitic carbon nitride coating prepared in Example 3 is shown below. Figure 3 As shown, the paper coating obtained through electrospinning and coating process, which is stacked layer by layer to cover paper fibers, can help enhance the antibacterial and hydrophobic effects of the product.

[0044] Scanning electron microscope image of the graphitic carbon nitride nanosheets prepared in Example 4 is shown below. Figure 4As shown, CNNS after thermal oxidation exfoliation exhibits a fragmented, sheet-like structure with a diameter ranging from 50 to 300 nm and a thickness between 5 and 10 nm. This reduction in physical size increases the specific surface area of ​​CNNS, increasing reactive sites and promoting the formation of more ROS. Furthermore, the thinner structure of CNNS reduces resistance during charge transport, effectively suppressing electron-hole recombination. Additionally, the transformation from CN to CNNS shortens the vertical distance for charge to move to the material surface, enhancing charge transfer and transport capabilities. These changes all contribute to enhancing the photocatalytic antibacterial effect.

[0045] The water contact angle diagram of the food packaging paper with a hydrophobic graphite-phase carbon nitride coating prepared in Example 5 is shown below. Figure 5 As shown, the maximum water contact angle reaches 145°, which is close to superhydrophobic and can meet the waterproof requirements during food packaging and transportation.

Claims

1. A method for producing graphite-phase carbon nitride electrospun antibacterial food packaging paper, characterized in that, The process includes the following steps: (1) preparing graphite phase carbon nitride by high-temperature calcination; (2) performing thermal oxidation stripping operation; (3) introducing hydrophobic materials to prepare coatings; and (4) preparing antibacterial food packaging paper by electrospinning device coating.

2. The production method as described in claim 1, characterized in that, The high-temperature calcination preparation of graphitic carbon nitride involves weighing 10-20 parts by weight of urea and calcining it in a tube furnace for 1-3 hours to obtain powdered graphitic carbon nitride.

3. The production method as described in claim 1, characterized in that, The high-temperature calcination was carried out under a nitrogen atmosphere.

4. The production method as described in claim 1, characterized in that, The high-temperature calcination is carried out at a rate of 2-8℃ / min, increasing the temperature from room temperature to 550℃.

5. The production method as described in claim 1, characterized in that, The thermal oxidation stripping operation is as follows: S1. Disperse the graphitic carbon nitride obtained by high-temperature calcination in deionized water; S2. Add 1-2 parts by mass of K2S2O8, stir thoroughly, and then adjust the pH to 12 with 0.1-1 mol / L KOH solution. S3. Stir the mixture prepared in S2 in a water bath at 80-100℃ for 6 h, then sonicate for 1-5 h, centrifuge to discard the supernatant, and wash the precipitate with deionized water until neutral. S4. After freeze-drying, g-C3N4 nanosheets were obtained.

6. The production method as described in claim 1, characterized in that, The hydrophobic material is a combination of PDMS and SiO2, specifically SiO2-PDMS.

7. The production method as described in claim 1, characterized in that, The coating is prepared by ultrasonically dispersing 20-30 parts of g-C3N4 nanosheets obtained by thermal oxidation exfoliation in 100 parts of n-hexane solvent, adding PDMS, hydrophobic nano-SiO2 and curing agent in a ratio of 10:2:1, and stirring until uniform.

8. The production method as described in claim 7, characterized in that, The curing agent is a dimethylsiloxane solution containing hydrogen-terminated groups.

9. The production method as described in claim 1, characterized in that, The electrospinning device described above is used to prepare food packaging paper by injecting the coating into the electrospinning solution chamber, setting the spinning voltage to 10-20kV, the spinning speed to 2-15mm / h, the receiving distance to 10-20cm, the needle diameter to 0.5-1.2mm, the syringe capacity to 10ml, and the spinning time to 1-5h. After drying in vacuum for 10-30h, hydrophobic graphite phase carbon nitride coated food packaging paper is obtained.

10. The production method as described in claim 1, characterized in that, The food packaging paper has a basis weight of 150-250 g / m³. 2 Corrugated paper.

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